Filter apparatus

ABSTRACT

Described is a filter apparatus (10) which is designed for filtering solid, liquid or gaseous, electrically uncharged or electrically charged particles out of a gaseous flow medium as it flows through the filter apparatus (10). The filter apparatus (10) has filter elements (18) which are spaced from each other in the direction of flow of the gaseous medium to the apparatus. Each filter element (18) has a plate-like carrier element (20, 46, 48; 64) and a substrate (22) which are provided with spaced-apart openings (26). The substrate (22) serves for the storage of a filter medium. Each opening (26) in the filter element (18) has a sleeve-like guide element (24) for the flow medium, wherein the guide element (24) extends around the edge of the corresponding opening (26). The guide elements (26) which project at least at the upstream side prevent filter medium at the individual substrates (22) from being unintentionally entrained through the openings (26), even at high flow rates in respect of the flow medium.

The invention relates to a filter apparatus for filtering solid, liquidor gaseous, electrically charged or electrically uncharged particles outof a gaseous flow medium which flows through the filter apparatus,comprising filter elements which are spaced from each other in thedirection of flow of the gaseous medium to the filter apparatus, whereineach filter element has a plate-like carrier element with spaced-apartopenings therethrough, the openings of adjacent plate-like carrierelements are displaced relative to each other in such a way that theyare not aligned with each other, and each plate-like carrier element hasat least on its upstream side a substrate which is provided for thestorage of a filter medium and which is provided with openingscorresponding to the openings in the associated plate-like carrierelement.

A filter apparatus of that kind is known from DE 36 37 428 Al. In thatarrangement the substrate which is provided for storage of the filtermedium comprises for example a foam material. The carrier elements forthe substrates may also be formed from a plastics material. That knownfilter apparatus uses in particular glycerine, to which furthersubstances may be added, as the filter medium.

DE 37 11 294 Al describes a filter apparatus of the kind set forth inthe opening part of this specification, in which the filter medium usedis for example glycerine or glycol or mixtures of those substances. Inthat known filter apparatus the filter medium is passed from acollecting container in a circuit to the spaced-apart filter elementswhich are arranged in succession in the direction of flow of the gaseousmedium to the apparatus. For that purpose, the apparatus has a conveyormeans for the filter medium. The plate-like carrier elements of theindividual filter elements are preferably in the form of plasticscarrier plates, with the substrates for storage of the filter mediumbeing disposed on the upstream sides thereof. The substrates arepreferably in the form of foam plates.

In all those known filter apparatuses, the openings in the individualfilter elements are in the form of through slots.

It has been found that the filter action of such filter apparatuses,with a given flow rate in respect of the gaseous flow medium to befiltered, through the filter apparatus, is better for heavy particleswhich are to be filtered than for light particles which are to befiltered. Furthermore, when carrying out operational tests in respect ofsuch filter apparatuses, it was found that the filter effect increaseswith an increasing rate of flow of the gaseous flow medium to befiltered, both for light particles to be filtered and also for heavyparticles. That means however that a relatively high rate of flow of thegaseous flow medium through the filter apparatus is a desirable aspect.The rate of flow of the gaseous flow medium has hitherto been limited inan upward direction by virtue of the fact that, at very high flow rates,particles of the filter medium can be entrained with the gaseous flowmedium which flows through the filter elements. That has at least anadverse effect on the desired filtering or cleaning action of the filterapparatus.

The invention is therefore based on the problem of so improving a filterapparatus of the kind set forth in the opening part of thisspecification, with simple means, that the filter or cleaning action ofthe filter apparatus is further improved.

In accordance with the invention, that problem is solved in thatthe/each plate-like carrier element comprises a material which isimpervious in relation to the filter medium, and that each opening inthe plate-like carrier element has a sleeve-like guide element for theflow medium, which extends around the edge of the opening and which isdirected at least approximately normal to the plate-like carrierelement.

By virtue of the fact that each plate-like carrier element, with theexception of the openings therein, is impervious to the filter medium,the filter medium is unable accidentally to pass through the plate-likecarrier elements. The sleeve-like guide elements for the flow mediumprovide the advantage that the particles of filter medium, which arepresent at the edge of the openings, are separated in space from thegaseous flow medium by the sleeve-like guide elements so that thoseparticles of the filter medium which are to be found at the edge of theopenings cannot be entrained with the gaseous flow medium which flowsthrough the openings, that is to say the sleeve-like guide elements.That provides a substantial improvement in the filter effect.

The/each guide element of the filter apparatus may be in the form of acollar which projects from the plate-like carrier element on theupstream side of the carrier element. In the case of a plate-likecarrier element comprising a sheet metal material, such a collar can beformed in a simple manner by a pressing operation, a deep drawingoperation or the like. It is even simpler for the/each guide element tobe in the form of a collar if the plate-like carrier element comprises aplastics material.

It has been found particularly advantageous for the guide element to beenlarged to form a flanged edge at its upstream front end which isremote from the plate-like carrier element. That flanged edge on theupstream front end of the guide element prevents particles of the filtermedium from accidentally passing through, even when using very high flowrates in respect of the gaseous flow medium. In that way it is possiblefor the filter apparatus to be operated at very high flow rates, incomparative terms, and it is thus possible for not only heavy but alsovery light, solid, liquid or gaseous, electrically charged orelectrically uncharged particles to be filtered out of the flow mediumas it flows through the apparatus.

As has already been indicated hereinbefore in connection with the guideelement in the form of a collar, the guide element can be made in onepiece with the plate-like carrier element. Such a configuration forthe/each guide element gives the advantage that the guide elements donot need to be produced in their own working operation and then joinedto the plate-like carrier elements in a further working operation. Sucha filter apparatus can accordingly be produced in a very simple andinexpensive manner.

In another configuration of the filter apparatus, the or each guideelement can be in the form of a sleeve element which passes through theassociated plate-like carrier element, one end portion of the sleeveelement projecting beyond the carrier element on the upstream side whilethe second end portion of the sleeve element projects beyond the carrierelement on the downstream side. When the filter apparatus is of such adesign configuration, the two end portions provide for an increase inthe change in direction of the gaseous flow medium, that is to say agreater degree of curvature in the flow path of the flow medium, andthus an improvement in the filter effect. In addition by suitabledimensioning of the individual guide elements or the spacing betweenadjacent filter elements, it is possible to achieve optimisation of theflow rate of the filter medium for the solid, liquid and/or gaseousparticles which are to be filtered out of the flow medium.

In a filter apparatus of the last-mentioned kind, that is to say in afilter apparatus in which the/each guide element is in the form of asleeve element passing through the associated plate-like carrierelement, it has been found advantageous for the/each guide element to bein the form of a venturi nozzle. Making the individual guide elements inthe form of venturi nozzles gives the advantage that the pressure dropfor the flow medium through the individual filter elements remains at acomparatively low level. Thus, with such a configuration of the filterapparatus, it is possible for the flow medium which flows through thefilter apparatus to be moved therethrough with a comparatively low levelof drive energy.

The/each guide element of the filter apparatus, that is to say eachindividual filter element of the filter apparatus, may have at least onefixing member with which the guide element is fixed in one of theopenings in the plate-like carrier element. Such a design isadvantageous in particular when the individual guide elements are notformed in one piece with the associated carrier element. Thelast-mentioned fixing members may be per se known snap-engagementretaining members, elements of a per se known bayonet-type securingarrangement, or the like.

In the above-described configurations of the filter apparatus, the/eachplate-like carrier element of the associated filter element is in onepiece with a given wall thickness, the wall thickness of the carrierelement being dependent on its dimensions in terms of surface area, theflow rate of the flow medium and the particles to be filtered out in theflow medium. A further embodiment of the filter apparatus according tothe invention is characterised in that the/each plate-like carrierelement has two spaced-apart outside walls which have mutually alignedapertures through which respective ones of the associated guide elementssealingly extend, wherein either the first outside wall on the upstreamside and the associated substrate or the second outside wall on thedownstream side is provided with through orifices which are spaced fromthe openings for the guide elements. If the first outside wall on theupstream side and the associated substrate of the/each filter element isprovided with through orifices, it is possible for particles which passthrough those orifices into the hollow space between the first andsecond outside walls to be removed from that space, thereby to provide aspecific filter effect. As the through orifices are to be provided inparticular in the vicinity of the openings for the guide elements, it ispossible with a filter apparatus of such a configuration for relativelyheavy particles to be filtered out of the flow medium which flowsthrough the filter apparatus. The lighter particles to be filtered out,which are transported with the flow medium, as well as the still heavierparticles, are deposited at the substrate and filtered out. That meansthat a specific filtration effect can be achieved in respect of a givensection of the mass spectrum of the particles to be filtered out, byvirtue of the through orifices in the first outside wall on the upstreamside and in the associated substrate. If it is only the second outsidewall on the downstream side that has through orifices of that kind, itis possible for example for a fluid medium to be introduced into thefilter apparatus through the hollow space between the first and secondoutside walls, and through the through openings provided in the secondoutside wall on the downstream side, in order as desired to moisten thegaseous flow medium which flows through the individual filter elementsand which is charged with particles to be filtered out.

It is also possible for an intermediate wall to be provided between thetwo outside walls of the/each plate like-carrier element, theintermediate wall forming two mutually separated central spaces, whereinthe intermediate wall and the two outside walls and the associatedsubstrate are provided with mutually aligned openings through which arespective one of the associated guide elements sealingly extends whilethe two outside walls and the associated substrate are provided withthrough orifices which are spaced from the openings for the guideelements, and the first central space which is defined by theintermediate wall and the first outside wall on the upstream side isprovided with an outlet member and the second central space defined bythe intermediate wall and the second outside wall on the downstream sideis provided with an inlet member. The solid, liquid or gaseous particlesto be filtered out, which are accumulated in the first central space,can be removed from the filter apparatus through the outlet member andfor example subjected to reprocessing. A liquid vapour or mist or agaseous medium for example can be introduced into the filter apparatusthrough the inlet member.

In a filter apparatus of the last-described kind, a cleaning means maybe provided between the inlet member associated with the second centralspace and the outlet member associated with the first central space. Theparticles which are filtered out of the gaseous flow medium and whichissue from the filter apparatus through the outlet member can be cleanedin the cleaning means, for example the solid materials may be separatedfrom the gaseous components of the particles to be filtered, whereuponthe gaseous components can be re-introduced into the filter apparatusthrough the inlet member. In that way it is possible to maintain thedesired pressure conditions in the filter apparatus.

The substrates which are provided for storage of the filter medium maycomprise for example a foam material, a foam ceramic, a metal mesh orthe like. The filter medium used may be glycerine, glycol or a mixtureof glycerine and glycol, while certain additives such as SiO₂, Al₂ O₃,perfumes or the like may be added to the filter medium.

Such a filter apparatus provides an excellent filter effect for solid,liquid or gaseous, charged or uncharged particles which are transportedwith a gaseous flow medium which is introduced into the filterapparatus. A further advantage is that such a filter apparatus has along operating or service life so that such a filter apparatus can beused without maintenance for example in relation to motor vehicles forproviding for a supply of fresh air.

At least some filter elements may be connected to a terminal of a dcvoltage source. In that way correspondingly charged ions can beattracted to the filter elements.

A further improved specific filter effect in respect of particles whichhitherto it has not been possible adequately to filter out is providedif the filter elements are combined together in groups, wherein eachindividual group of filter elements has associated therewith its owncollecting, conveyor and discharge means. By virtue of the filterapparatus being of such a configuration, it is possible for theindividual groups of filter elements to be wetted with different filtermedia. With different filter media of that kind, it is possible for thesolid, liquid or gaseous particles of noxious material which aretransported with the gaseous flow medium flowing through the filterapparatus to be filtered out of the flow medium in a controlled mannerin the individual groups of filter elements. In addition, with such afilter apparatus, it is possible to use different filter media which arenot compatible with each other. In such a situation it is of coursepossible for the different filter media to be retained in the associatedgroups of filter elements, that is to say, to be limited to thosegroups.

It has been found to be advantageous for at least individual groups offilter elements to be provided with their own respective cooling and/orheating means for the associated filter medium. With such cooling orheating means, it is possible for the filter media associated withindividual groups of filter elements to be kept at the respectivetemperature which is the optimum one for the filter medium, whiledifferent filter media of the filter apparatus can be heated to orcooled down to different temperatures.

At least some of the groups of filter elements may be provided withtheir own cleaning or regenerating means for the associated filtermedium. With such a cleaning means it is possible for the filter mediumof the corresponding group of filter elements to be removed from thefilter apparatus and cleaned in the cleaning means and for the cleanedfilter medium to be restored to the filter apparatus. It is likewisepossible to regenerate an exhausted filter medium by means of theregenerating means, and to restore it to the filter apparatus in aregenerated condition. A filter apparatus of the last-mentioned kindthus gives the advantage of having a very long service life.

The filter medium is preferably glycerine, glycol or a mixture ofglycerine with glycol, while additives of for example SiO₂, Al₂ O₁,perfume substances or the like may be added to such a filter medium. Atleast one filter medium for at least one group of filter elements maycontain a culture of enzymes. It is likewise possible for at least onefilter medium to contain a bacterial culture. Depending on the particlesof noxious material which are to be filtered out by means of the filterapparatus, at least one filter medium of at least one group of filterelements may also contain microorganisms. By virtue of such enzymeand/or bacterial cultures or microorganisms, it is possible forparticles of noxious material to be filtered out in a controlled mannerin the individual filter elements or groups thereof, so that the resultis a filter apparatus with excellent filtration properties. Such filtermedia may also be suitable for converting the aggregate condition ofparticles of noxious material so that it is possible for example bymeans of microorganisms to convert liquid particles of noxious materialinto gaseous form.

A survival storage means is preferably provided for the respectiveorganic filter medium. The purpose of such a survival storage means isto keep the respective organic filter medium alive and thus effective,if the filter apparatus is not in use for a given period of time, sothat the organic filter medium is not supplied with the substancesrequired for it to survive. During that period of time the respectiveorganic filter medium is supplied with the substances required for it tocontinue to survive, by means of the survival storage means.

It has been found advantageous to provide a housing which is of avarying internal cross-section between an inlet and an outlet, along thelongitudinal extent of the housing, wherein the filter elements orgroups of filter elements arranged in the housing are each of a surfacearea corresponding to the corresponding internal cross-section of thehousing. In that way it is possible for the flow medium which flowsthrough the filter apparatus to flow through the filter elements orgroups of filter elements at different rates. In that way the speed ofthe gaseous flow medium which is charged with particles of noxiousmaterial in the individual filter elements or groups of filter elementscan be adapted in the optimum fashion to the particles of noxiousmaterial which are to be filtered out in a controlled manner in thosefilter elements or groups thereof. Suitable selection in respect of thefilter medium in each individual group of filter elements and suitableselection in respect of the rate of flow of the gaseous flow medium inthe corresponding group of filter elements makes it possible for theindividual solid, liquid or gaseous particles of noxious material to befiltered out of the flow medium in a specific and optimum fashion in thesuccessively disposed groups of filter elements. That arrangementprovides a filter apparatus with excellent filtration properties andwith the further considerable advantage that widely differentcombinations of filter media and flow rates can be combined so that sucha filter apparatus can be employed over a wide area of use.

The internal cross-section of the housing preferably decreases in adirection from the inlet to the outlet of the filter apparatus. In thatway the rate of flow of the flow medium in the filter apparatusincreases from one group of filter elements to the next group or thesubsequent groups so as to provide a very good filter effect. Morespecifically, it has been found that, with a constant rate of flow ofthe flow medium, heavy particles of noxious material are filtered outbetter than lighter particles. On the other hand it was found inoperational tests that the filter effect in respect of particles ofnoxious material of a given mass, that is to say a given weight, becomesprogressively better with an increasing rate of flow of the flow medium.That means that it is desirable to use the highest possible rate offlow. The rate of flow of the flow medium however is limited in anupward direction by the structure of the filter apparatus and thematerials used for the filter elements. It is therefore desirable forthe heavy particles of noxious material to be first filtered out in thegroups of filter elements which are adjacent to the inlet of the filterapparatus, with a comparatively low flow rate being sufficient for thatpurpose, while the light particles of noxious material are only thenfiltered out of the flow medium as it flows through the filterapparatus, in groups of filter elements which are further away from theinlet, which is made possible by increasing the flow rate.

The internal cross-section of the housing may decrease continuously orpreferably in a stepwise manner in a direction from the inlet to theoutlet. A stepwise configuration of the housing gives the advantage thatthe filter elements of the groups associated with the individual stepsare of the same size so that the expenditure involved in regard tomanufacture of the filter elements or groups of filter elements isimmaterial.

The filter apparatus according to the invention may be used in anydesired position. It has been found advantageous however for the filterapparatus to be used in a horizontal position, that is to say thelongitudinal extent of the housing, which is defined between the inletand the outlet of the housing of the filter apparatus, is directed atleast approximately horizontally. In that case the filter elements arepreferably arranged at an inclined angle from the top front towards thebottom rear, relative to the longitudinal axis of the housing, whichextends between the inlet and the outlet. That angle of inclination ispreferably adapted to the resultant which is defined by the horizontallyextending component of the flow rate of the flow medium and the verticalgravitational component. That inclined arrangement of the filterelements or groups of filter elements thus prevents liquid filter mediumfrom accidentally dripping off the individual filter media of the groupsof filter elements.

The angle of inclination of the individual filter elements or the angleof inclination of the filter elements of the various groups of filterelements may be variable or set in dependence on the rate of flow of theflow medium to and through the filter elements. When the angle ofinclination is fixed and invariable, that arrangement provides only foran average approximation or adaptation to the rate of flow of the flowmedium through the apparatus. If the angle of inclination is variable,it is possible to provide for a precise adaptation effect. Thefirst-mentioned case means that the filter apparatus is of a simplerdesign than the last-mentioned case with a variable angle ofinclination.

Further details, features and advantages will be apparent from thefollowing description of embodiments of the filter apparatus accordingto the invention, as illustrated in the drawing in which:

FIG. 1 is a partly sectional side view on a reduced scale of a filterapparatus,

FIG. 2 is a view on an enlarged scale of the detail II in FIG. 1,

FIG. 3 is a sectional view of a portion of an embodiment of a filterelement,

FIG. 4 is a sectional view corresponding to FIG. 3 of a secondembodiment of a filter element of which a portion is shown,

FIG. 5 is a view in longitudinal section through two adjacent filterelements of which portions are shown,

FIG. 6 is a view corresponding to FIG. 5 through another embodiment oftwo adjacent spaced-apart filter elements,

FIG. 7 is a view in longitudinal section through a further embodiment ofa filter element of the filter apparatus, showing a portion of thefilter element, and

FIG. 8 is a view corresponding to FIG. 1 of a second embodiment of thefilter apparatus.

FIG. 1 shows a filter apparatus 10 having a housing 12 comprising aninlet connection 14 and an outlet connection 16. A gaseous flow mediumis introduced into the filter apparatus 10 through the inlet connection14. The flow medium is charged with solid, liquid and/or gaseousparticles which are to be filtered out of the gaseous flow medium, thatis to say separated therefrom, by means of the filter apparatus 10. Forthat purpose the filter apparatus 10 has a number of filter elements 18which are arranged in succession at spacings from each other in thehousing 12. The filter elements 18 are described in detail hereinafterwith reference to FIGS. 2 to 7.

FIG. 1 shows some filter elements 18 in a filter apparatus which isdisposed horizontally, the filter elements being shown as standing atleast approximately vertically. It will be appreciated that it is alsopossible for the filter apparatus 10 to be disposed and operated in anyother position. For example it would be possible for the filterapparatus 10 to be arranged vertically so that the filter elements 18are arranged in horizontal planes which extend above or below eachother. In that case it is necessary for the inlet connection 14 to bearranged at the top and for the outlet connection 16 to be arranged atthe bottom. That is related to the fact that the guide elements whichare described in detail hereinafter project away at least from theupstream side of the individual filter elements, as will be made clearhereinafter with reference to FIGS. 2 to 7.

FIG. 2 shows two filter elements 18 which are arranged at a spacing fromeach other and in succession and each of which has a plate-like carrierelement 20 of a material which is impervious to the filter medium, and asubstrate 22 for storage of the filter medium. The substrate 22 isprovided on the upstream side of the associated plate-like carrierelement 20. The carrier element 20 may be a member of sheet metal, aplastics plate or the like. The substrate 22 may comprise a plasticsfoam material, a foam ceramic, a wire mesh or the like. Each plate-likecarrier element 20 is provided with guide elements 24 which project fromthe carrier element 20 on the upstream side thereof and which are in theform of a collar. The collar-like guide elements 24 define throughopenings 26 through which the gaseous medium flows through theindividual filter elements 18. Thin curved lines 28 in FIG. 2diagrammatically indicate the flow of the gaseous flow medium betweenadjacent filter elements 18, that is to say between mutually displacedopenings 26 in adjacent filter elements 18. The line 30 diagrammaticallyindicates the trajectory of relatively heavy particles, with the radiusof curvature of that trajectory being relatively large as a result ofthe comparatively high mass of the particles.

The line 32 identifies the trajectory of a somewhat lighter particle,with the particles which pass along the lines 30 and 32 meeting thesubstrate 22 and being retained by means of the filter medium on or inthe substrate 22, at the filter element 18. That provides for particlesbeing filtered out of the gaseous flow medium. By suitable dimensioningof the spacing between adjacent filter elements 18, the spacing betweenadjacent openings 26 which are arranged for example in the form of agrid matrix, the diameter of the openings 26 and the flow rate of thegaseous flow medium through the filter apparatus, that is to say throughthe individual filter elements 18, it is possible for the solid, liquidand/or gaseous particles which are transported with the gaseous flowmedium to be filtered out of same.

As the collar-like guide elements 24 project beyond the associatedsubstrate 22 with their upstream front end 34 which is remote from theassociated plate-like carrier element, the filter medium on eachsubstrate 22 is prevented from being entrained through the individualopenings 26 by the gaseous flow medium. Accordingly the loss of filtermedium is negligibly low so as to provide a maintenance-free filterapparatus.

FIG. 3 shows a portion of a plate-like carrier element 20 of a filterelement 18, which is provided with collar-like guide elements 24 ofwhich only one is shown. The collar-like guide element 24 projects awayfrom the upstream side of the plate-like carrier element 20 at leastapproximately perpendicularly, with the collar-like guide element 24defining an opening 26. The gaseous flow medium which is charged withsolid, liquid or gaseous particles to be filtered out can flow throughthe opening 26. As described hereinbefore with reference to FIG. 2,different particles are filtered out at the individual filter elements18 (see the lines 30 and 32 in FIG. 2). For that purpose each filterelement 18 is provided with a substrate 22 which is disposed on theupstream side of the associated carrier element 20. In the embodiment ofthe filter element 18 shown in FIG. 3, the individual collar-like guideelements 24 are of an axial dimension which is greater than the wallthickness of the substrate 22 having the filter medium. In theconstruction shown in FIG. 3 the collar-like guide element 24 isenlarged to form a flanged edge 36 at its front end 34 on the upstreamside, which is remote from the plate-like carrier element 20. Theflanged edge 36 provides a further improved retaining effect for thefilter medium in or on the substrate 22 so that, even at very high flowrates in respect of the gaseous flow medium flowing through the openings26, the filter medium is not entrained through the openings 26. Thatprovides a further improvement in the filter effect and at the same timea further improvement in regard to freedom from maintenance of a filterapparatus equipped with such filter elements 18.

FIG. 4 is a sectional view of a portion of a filter element 18 in whichthe/each guide element projects with a first end portion 38 on theupstream side beyond the plate-like carrier element 20 or the substrate22 for the filter medium, and wherein a second end portion 40 projectsbeyond the plate-like carrier element 20 on the downstream side. In thatarrangement the guide element 24 is in the form of a venturi nozzle,that is to say the opening 26 is of a venturi nozzle-like configuration.With that configuration of the/each filter element 18, the front end 34is also provided with a flanged edge 36 in order reliably to preventaccidental entrainment of filter medium in/on the substrate 22. Fixingmembers 42 and 44 serve for mechanically fixing the individual guideelements 24 to the associated filter elements 18. The fixing members 44are in the form of projections which extend around the associated guideelements 24 and the fixing members 42 can be for example in the form ofknob-like raised portions. In order to ensure that the guide elements 24are fixed to the individual filter elements 18 with such fixing members42 and 44, the associated plate-like carrier elements 20 and thecorresponding substrates 22 may be provided with longitudinal recesseswhich extend in the axial direction and which correspond to theknob-shaped fixing members 42, thereby providing per se knownbayonet-type fixing arrangements. If the material of the guide elements24 is sufficiently elastically yielding, the guide elements 24 may alsobe fixed in position by simple snap-engagement retaining action. Guideelements 24 of a venturi nozzle-like configuration give the particularadvantage that the pressure drop in respect of the gaseous flow mediumwhich flows through the openings 26 is comparatively low, even atrelatively high flow rates, so that the drive energy for passing theflow medium through the filter apparatus can be relatively low.

FIG. 5 shows views in longitudinal section of portions of two filterelements 18 which are arranged in succession and at a spacing from eachother, in which each plate-like carrier element has two spaced-apartoutside walls 46 and 48, defining a central space 50 between them. Thetwo outside walls 46 and 48 have mutually aligned apertures 52. Asubstrate 22 for a filter medium is provided on the front side of thefirst outside wall 46, on the upstream side, of each filter element 18.Each substrate 22 has apertures 54 corresponding to the apertures 52 inthe outside walls 46, in regard to their distribution and size. Theassociated guide elements 24 extend sealingly through the apertures 52in the outside walls 46 and 48 and through the apertures 54 in theassociated substrate 22. This construction also provides that the guideelements 24 have an enlarged flanged edge 36 at their front end 34 onthe upstream side. Reference numeral 28 again identifies flow lines ofthe gaseous flow medium which is charged with particles and which flowsthrough the individual openings 26 in the successively arranged,spaced-apart filter elements 18. As in FIG. 2, reference numerals 30 and32 identify the trajectories of heavy particles which are to be filteredout of the gaseous flow medium and which are retained at the substrate22 by means of the filter medium.

In the embodiment of the filter apparatus as shown in FIG. 5 thedownstream second outside walls 48 of the individual filter elements 18have through orifices 56 which are spaced from the apertures 52. Thethrough orifices 56 make it possible for a medium to pass from thecentral space 50 of the individual filter elements 18 into the filterspace 58 disposed between the filter elements 18. The arrows 60 indicatethe way in which a medium issues from the central space 50 of eachindividual filter element 18. That medium may be for example a fluidmist which can condense on particles to be filtered out and which thusmakes those particles heavier so as to provide a good filter effect.

FIG. 6 shows a portion of a filter apparatus which differs from theportion shown in FIG. 5 in that it is not the second outside walls 48,which are on the downstream side, of the carrier elements of thespaced-apart and successively disposed filter elements 18 that areprovided with through orifices 56 (see FIG. 5), but the first outsidewalls 46 on the upstream side and the substrates 22 which are disposedon the front side of the first outside walls 46. In the constructionshown in FIG. 6, the substrates 22 and the first outside walls 46 areprovided with through orifices 62 which are spaced from the openings 26of the filter elements 18. Reference numeral 28 in FIG. 6 alsoidentifies some flow lines of the gaseous flow medium, along which thegaseous flow medium flows through the openings 26 in adjacent filterelements 18. Reference numerals 30 and 32 identify trajectories ofparticles of different weights, which are transported with the gaseousflow medium and which are to be separated from the gaseous flow mediumin order to be filtered out of same. Heavy particles pass along thetrajectory 30 and are retained at the substrate 22 by means of thefilter medium on the substrate. Somewhat lighter particles move alongthe trajectory 32 and are deflected towards the through orifices 62 andpass through the orifices 62 into the central space defined by theoutside walls 46 and 48 of each filter element 18. In that way it ispossible for given particles to be separated out of the filter apparatusin a specific fashion at given locations.

FIG. 7 shows an embodiment of a filter element 18 wherein providedbetween the first outside wall 46 on the upstream side and the secondoutside wall 48 on the downstream side is an intermediate wall 64 whichdivides the central space into two mutually separated central spaces 66and 68. This construction also provides that there is a substrate 28 fora filter medium on the upstream side of the first outside wall 46. Theopenings 26 which are delimited by means of guide elements 18 passthrough the substrate 22, the two outside walls 46 and 48 and theintermediate wall 64 of the corresponding filter element 18. Inaccordance with the embodiment illustrated in FIG. 6, the substrate 22and the first outside wall 46 of each filter element 18 has throughorifices 62 which provide a fluid communication between the filter space58 and the first central space 66. In accordance with the constructionshown in FIG. 5, in the embodiment illustrated in FIG. 7 the secondoutside wall 48 is also provided with through orifices 56 which producea fluid communication between the second central space 68 and the filterspace 58. The first central space 66 is provided with an outlet member70 which is only diagrammatically indicated in FIG. 7. An inlet member72 is diagrammatically indicated by a box which is in fluidcommunication with the second central space 68. Provided between theoutlet member 70 and the inlet member 72 is a cleaning means 74connected to the inlet and outlet members 72 and 70 by means of conduits76. The particles collected in the first central space 66 can be cleanedin the cleaning means 74, while for example solid components of theparticles which are filtered out are separated from gaseous componentsthereof. The gaseous components can then be passed through the inletmember 72 into the second central space 68 and through the orifices 56into the filter space 58 so that the pressure drop in the filterapparatus remains negligibly low.

FIG. 8 shows a filter apparatus comprising a housing 12 having an inletconnection 14 and an outlet connection 16. A gaseous flow medium isintroduced into the filter apparatus through the inlet connection 14.The gaseous flow medium is charged with solid, liquid or gaseousparticles which are to be filtered out of the gaseous flow medium, thatis to say separated therefrom, by means of filter elements 18 disposedin the filter apparatus 10. The filter elements 18 are combined togetherto form groups, wherein each individual group of filter elements hasassociated therewith its own collecting means 1, its own conveyor means2 and its own discharge means 3. Each collecting means 1 is in fluidcommunication with the associated conveyor means 2 by means of a conduit4, which conveyor means 2 may be a pump. The conveyor means 2 is influid communication with the associated discharge means 3, by means of aconduit 4a. A cooling or heating means 5 is connected into the conduit4a of the each group of filter elements, whereby the filter medium whichpasses in a circuit or which is circulated by the conveyor means 2 canbe cooled or heated as desired in order for the filter medium to be keptat an optimum temperature for filtration purposes. In addition acleaning or regenerating means 6 is connected into each conduit 4a of acorresponding group of filter elements. Reference numeral 7 denotes asurvival storage means which is connected into a conduit 4a. Twochange-over switching means 8 and 9 are connected together by means of aby-pass conduit 4b and are connected into the conduits 4 and 4a, whichhave the survival storage means 7, of the third circuit shown at theright in FIG. 8. FIG. 8 shows a housing 12 of the filter apparatus 10,the internal cross-section of which varies in a stepwise manner betweenthe inlet 14 and the outlet 16, that is to say, it decreases in astepwise manner. In that way the flow rate of the flow medium betweenthe first group of filter elements at the left and the third group offilter elements at the right becomes correspondingly greater in astepwise manner. It will also be seen from this figure that the angle ofinclination of the filter element of the various groups of filterelements increased in accordance with the increasing rate of flow of theflow medium. The individual groups of filter elements 18 may be suppliedwith the same filter medium or preferably with different filter media.That is possible because the individual groups of filter elements eachhave their own circuit for the corresponding filter medium.

A description of the individual collecting means and the discharge meanscan be found for example in DE 37 11 294 Al. Likewise there should be noneed for the cooling or heating means 5, the cleaning or regeneratingmeans 6 and the survival storage means 7 to be described in detailherein because those means are known per se. The survival storage means7 is connected to the associated conveyor means 2, the associatedcooling or heating means 5 and the associated cleaning or regeneratingmeans 6 by the conduits 4a and 4b when the two change-over switchingdevices 8 and 9 are in the appropriate switching position. In thatswitching position of the devices 8 and 9, the fluid communication withthe associated discharge means 3 and the communication between theassociated collecting means 1 and the change-over switching device 9 areinterrupted. It is also possible however for the survival storage means7 to be in fluid communication with the corresponding discharge means 3in order to provide in the filter elements 18 of the associated group offilter elements for a feed of the filter medium in that group, for thefilter medium to survive while the filter apparatus 10 is not in useover a prolonged period of time.

I claim:
 1. A filter apparatus for filtering solid, liquid, or gaseous,electrically charged or electrically uncharged particles out of agaseous flow medium which flows through the filter apparatus, comprisingfilter elements (18) which are spaced from each other in the directionof flow of the gaseous medium to the filter apparatus, wherein eachfilter element (18) has a plate-like carrier element (20; 46; 48; 64)with spaced-apart openings (26) of adjacent plate-like carrier elementsare displaced relative to each other in such a way that they are notaligned with each other, and that each plate-like carrier element (20;46; 48; 66) has at least on its upstream side a substrate (22) which isprovided for the storage of a filter medium and which is provided withopenings (26) corresponding to the openings (26) in the associatedplate-like carrier element, characterized in that each plate-likecarrier element (20; 46; 48; 66) comprises a material which imperviousin relation to the filter medium, and that each opening (26) in theplate-like carrier element has a sleeve-like guide (24) for the flowmedium, which extends around the edge of the opening (26) and extendsover the upstream side of the respective substrate, and which isdirected at least approximately normal to the plate-like carrierelement.
 2. A filter apparatus according to claim 1 characterised inthat the/each guide element (24) is in the form of a collar whichprojects from the plate-like carrier element (20) on the upstream sideof the carrier element (20).
 3. A filter apparatus according to claim 1wherein said guide element (24) is enlarged to form a flanged edge (36)at its front end (34) on the upstream side, which is remote from theplate-like carrier element (20).
 4. A filter element according to claim1 wherein said guide element (24) is formed in one piece with theplate-like carrier element (20).
 5. A filter apparatus according toclaim 1 characterised in that the/each guide element (24) is in the formof a sleeve element which passes through the associated plate-likecarrier element (20; 46, 48; 64), one end portion (38) of the sleeveelement projecting beyond the carrier element on the upstream side andthe second end portion (40) of the sleeve element projecting beyond thecarrier element on the downstream side thereof.
 6. A filter apparatusaccording to claim 5 characterised in that the/each guide element (24)is in the form of a venturi nozzle.
 7. A filter apparatus according toclaim 5 wherein each guide element (24) has at least one fixing member(42,44) with which the guide element (24) is fixed in one of theopenings (26) in the plate-like carrier element (20; 46; 48; 64).
 8. Afilter apparatus according to claim 1 wherein each plate-like carrierelement has two spaced-apart outside walls (46,48) which have mutuallyaligned apertures (52) through each of which a respective one of theassociated guide elements (24) sealingly extends, wherein either thefirst outside wall (46) on the upstream side and the associatedsubstrate (22) or the second outside wall (48) on the downstream side isprovided with through orifices (56;62) which are spaced from theopenings (26) for the guide elements (24).
 9. A filter apparatusaccording to claim 8 characterised in that provided between the twooutside walls (46, 48) of the/each filter element (18) is anintermediate wall (64) which forms two mutually separated central spaces(66, 68), wherein the intermediate wall (64) and the two outside walls(46, 48) and the associated substrate (22) have mutually aligned throughopenings (26), through each of which a respective one of the associatedguide elements (24) sealingly extends, that both outside walls (46, 48)and the associated substrate (22) have through orifices (52, 54) whichare spaced from the openings (26) for the guide elements, and that thefirst central space (66) defined by the intermediate wall (64) and thefirst outside wall (46) on the upstream side is provided with an outletmember (70) and the second central space (68) defined by theintermediate wall (64) and the second outside wall (48) on thedownstream side has an inlet member (72).
 10. A filter apparatusaccording to claim 9 characterised in that a cleaning means (74) isprovided between the inlet member (72) associated with the secondcentral space (68) and the outlet member (70) associated with the firstcentral space (66).
 11. A filter apparatus according to claim 1 whereinat least individual filter elements (18) are connected to a terminal ofa DC voltage source.
 12. A filter apparatus according to claim 1 whereinthe filter elements (18) are combined together to form groups, whereineach individual group of filter elements has associated therewith itsown collecting, conveyor, and discharge means (1,2,3).
 13. A filterapparatus according to claim 12 characterised in that the individualgroups of filter elements are wetted with different filter media.
 14. Afilter apparatus according to claim 12 wherein at least individualgroups of filter elements are provided with their own respective coolingand/or heating means (5) for the associated filter medium.
 15. A filterapparatus according to claim 12 wherein at least some of the groups offilter elements are provided with their own cleaning or regeneratingmeans (6) for the associated filter medium.
 16. A filter apparatusaccording to claim 12 wherein at least one filter medium contains aculture of enzymes.
 17. A filter apparatus according to claim 12 whereinat least one filter medium contains a bacterial culture.
 18. A filterapparatus according to claim 12 wherein at least one filter mechanismcontains microorganisms.
 19. A filter apparatus according to claim 16wherein a survival storage means (7) is provided for the filter medium.20. A filter apparatus according to claim 12, and further comprising ahousing (12) which is of a varying internal cross-section between aninlet (14) and an outlet (16) along the longitudinal extent of thehousing, wherein the filter elements (18) or groups of filter elementsarranged in the housing (12) are each of a surface area corresponding tothe corresponding internal cross-section of the housing (12).
 21. Afilter apparatus according to claim 20 characterised in that theinternal cross-section of the housing (12) decreases in a direction fromthe inlet (14) to the outlet (16).
 22. A filter apparatus according toclaim 20 wherein the internal cross-section of the housing (12)decreases in a stepwise manner in a direction from the inlet (14) to theoutlet (16).
 23. A filter apparatus according to claim 1 wherein thefilter elements (18) are of a flat configuration and are arrangedinclinedly at an angle of inclination from the top front towards thebottom rear relative to the longitudinal axis of the housing (12), whichextends between the inlet (14) and the outlet (16).
 24. A filterapparatus according to claim 23 characterised in that the angle ofinclination is variable or is set in dependence on the flow rate of theflow medium to and through the filter apparatus.